Rainer Reinscheid, a 48-year-old an associate professor of pharmaceutical science, was arrested July 24 after Irvine police found him trying to start a fire using lighter fluid and newspaper in the Mason Park Preserve near University High School, the Orange County district attorney's office said.

Police had increased patrols in the University High School area after a series of small fires in and around the school started July 4, said Irvine police Lt. Julia Engen. The fires did not injure anyone or burn down any structures but left school property scorched, and police feared that another fire might ignite the preserve's dry brush and cause a major conflagration.

But when investigators looked at Reinscheid's cellphone, what they found, they said, was far more troubling.

In emails from April addressed to himself and his wife, Reinscheid allegedly planned to obtain firearms to murder students and administrators, commit sexual assault, burn down the school and then kill himself, said Farrah Emami, spokeswoman for the Orange County district attorney's office.

"We did take these emails very seriously," Emami said.

The professor — who posted bail and was released after his intial arrest — was taken into custody again and is now being held without bail, which prosecutors requested in court Tuesday. He faces felony arson charges.

Reincheid's 14-year-old son, Claas Stubbe, attended University High School. The teenager committed suicide in March, days after he was disciplined by school administrators for what Irvine Unified School District spokesman Ian Hanigan described as a "fairly minor" matter involving a theft from a student store. He was given trash pickup duty as a punishment.

Acquaintances say Reinscheid had been furious at University High School for how it handled his son's death.

"He was angry and unsatisfied with the investigation into his son's death," said Bruce Blumberg, a professor in Reinscheid's department at UC Irvine. Blumberg described Claas Stubbe as "a sweet and sensitive boy."

There were rumors the boy had been bullied, though Hanigan maintained that no evidence was found to support the claim. Irvine police said they were unable to verify what drove him to suicide.

"There is just a tragic situation for [Reinscheid] and his family," Engen said, but added: "This is such an irrational response. … This is not a normal grieving."